A 32-year-old woman presents to the psychiatric nurse practitioner with a 3-month history of concentration difficulty, irritability, and depression. She has not experienced these symptoms at any other time in her life. During an extensive history inquiry, the woman states that 4 months prior to her visit with the nurse practitioner, she had experienced a short-term flu-like illness and noticed a bull's eye-shaped rash on her calf. She has noted no other symptoms since then, until the mood symptoms began. Her physical examination and laboratory findings are within normal limits. Which of the following is the most likely diagnosis?

Choice A reason: Syphilis can cause neuropsychiatric symptoms in tertiary stages but is unlikely with an acute bull’s eye rash and flu-like symptoms preceding mood changes. Choice B reason: Chronic fatigue syndrome is characterized by prolonged fatigue lasting at least 6 months, often with cognitive impairment, but does not usually present with a recent erythema migrans rash. Choice C reason: This is correct. The patient’s history of a flu-like illness and a bull's eye-shaped rash (erythema migrans) is characteristic of early Lyme disease. Post-infectious neuropsychiatric symptoms such as depression and irritability may develop weeks to months after initial infection. Choice D reason: Adult ADHD would present with long-standing attention deficits from childhood, not a sudden onset following an infectious illness.